1. Field of the Invention
The present invention relates to a rotary sensor capable of detecting a rotation angle transmitted from outside used as a throttle sensor of an automobile, for example.
2. Description of the Related Art
Drawings of a rotary sensor according to the related art will now be described. FIG. 14 is a front view of a rotary sensor according to the related art. FIG. 15 is a sectional view taken along the line 15—15 in FIG. 14. FIG. 16 is a perspective view of a spring member of the rotary sensor according to the related art.
Referring to the rotary sensor according to the related art based on FIGS. 14 to 16, a housing 51 is constituted by a case 52 that is a part molded from synthetic resin and a lid 53 that closes an opening of the case 52 located on the rear side of the same.
The case 52 has a cylindrical side wall 52b having a container section 52a therein, a receiving section 52c that is a cylindrical section protruding into the container section 52a from the sidewall 52b, and a cylindrical section 52e formed such that it extends perpendicularly from the side wall 52b. 
The lid 53 has a dish-like configuration and has a plate-like section 53a and a flange section 53b provided at the periphery of the plate-like section 53a. 
The lid 53 is attached to the case 52 to close the opening by thermally caulking a rear part of the side wall 52b of the case 52.
A plurality of terminals 54 made of metal is used for a connector. The terminals 54 are embedded and mounted in the case 52 such that one end of each terminal protrudes into the container section 52a of the case 52 and such that the other end protrudes into the cylindrical section 52e. 
A plate-like insulated substrate 55 has a hole 55a in the middle thereof, and a resistor pattern and a collector pattern made of a highly conductive material are provided on one surface of the insulated substrate 55 although not shown. The resistor pattern and the collector pattern are in conduction to the plurality of terminal sections 56 attached to the insulated substrate 55.
The insulated substrate 55 is contained in the container section 52a with a peripheral part of the same placed on a step section 52d, and the terminal sections 56 are solder-connected to the terminals 54 for a connector protruding into the container section 52a. 
A rotary body 57 that is a part molded from synthetic resin has a disk-shaped section 57a, a cylindrical wall section 57b forwardly protruding from the center of the disk-shaped section 57a, a recess 57c provided in the middle of the cylindrical wall section 57b, a groove section 57d that is a substantially rectangular small recess formed contiguously to the recess 57c, and a protrusion 57f formed such that it protrudes from the disk-shaped section 57a rearward. The disk-shaped section 57a is also provided with a slider 57e formed from a conductive metal.
The rotary body 57 is contained in the container section 52a of the case 52. The cylindrical wall section 57b is in contact with the receiving section 52c, and the protrusion 57f is rotatably inserted in the hole 55a of the insulated substrate 55. When the rotary body 57 rotates, the slider 57e slides on the resistor and the collector to change the value of an output voltage.
The spring member 58 is formed by processing a metal plate, and it has a substantially plate-like base section 58a and an elastic piece 58b formed by bending an end of the base section 58a in the form of the character V. The spring member 58 has very small dimensions, and it is press-fitted and mounted in the groove section 57d of the rotary body 57.
A driving shaft 59 is in the form of a non-circular rod body and is press-fitted in the recess 57c of the rotary body 57 at a rear end thereof. A side of the driving shaft 59 is elastically pressed by the elastic piece 58b of the spring member 58 to be held by an elastic pressure. The driving shaft 59 can rotate the rotary body 57 within a predetermined range of rotation angles.
The driving shaft 59 is linked with a throttle valve of an automobile. When the driving shaft 59 rotates, the rotary body 57 rotates to cause the slider 57e to slide on the resistor and the collector consequently, which causes a change in the output voltage to enable detection of a rotation angle of the valve.
While the rotary sensor according to the related art is configured and operates as described above, it has a problem in that mass-productivity is low because the configuration for holding the driving shaft 59 with an elastic pressure using the spring member 58 press-fitted in the narrow groove section 57d requires an operation of press-fitting the small spring member 58 into the groove section 57d during assembly which reduces the ease of operation and assembly. The groove section 57d is provided on the rotary body 57 in addition to the recess 57c, which requires complicated processing and increases the size of the rotary body 57, resulting in another problem in that the sensor as a whole becomes large.
A rotary sensor according to the invention has been made taking such problems into consideration, and there is provided a compact rotary sensor that is easy to assemble by improving the shape and mounting of the spring member.
(1) In order to solve the above problems, a rotary sensor according to the invention has a housing, a rotary body rotatably supported in the housing, a detection unit operated by rotating the rotary body, and a driving shaft inserted in a recess formed on the rotary body for rotating the rotary body, and it has a configuration in which a spring member made of metal having at least a pair of arm sections and a connecting section connecting the arm sections is disposed in the recess of the rotary body and in which the driving shaft is sandwiched and held by the pair of arm sections with an elastic pressure applied thereto.
(2) The recess of the rotary body of the rotary sensor according to the invention has wall sections facing each other, and the pair of arm sections are in elastic contact with the wall sections.
(3) At least either of the arm sections of the rotary sensor according to the invention has an elastic piece that is bent to extend toward the connecting section, and the driving shaft is in elastic contact with the elastic piece.
(4) An inclined portion extending toward the arm section is provided on the elastic piece of the rotary sensor according to the invention.
(5) A protrusion is provided in the recess of the rotary sensor according to the invention, and at least either of the arm sections is provided with a slit extending in the axial direction of the driving shaft across the connecting section and the arm section, the slit being engaged with the protrusion.
(6) The spring member of the rotary sensor according to the invention forms a substantially U-like configuration in combination with the pair of arm sections and the connecting section, and the pair of arm sections are in a symmetrical configuration.
(7) The arm sections have base portions in a face-to-face relationship with the wall section of the rotary body, and reinforcement units for preventing the deformation of the base portions are provided at the base portions.
(8) The base portions have ribs formed to extend in the axial direction of the driving shaft, and the reinforcement units are constituted by the ribs.
(9) The ribs are formed such that they bulge out toward the wall sections.
(10) The base portions have bent pieces formed such that they extend in the axial direction of the driving shaft, and the reinforcement units are constituted by the bent pieces.
(11) The bent pieces are bent toward the wall sections.
(12) The base portions have hardened parts which have been hardened through a punching process, and the reinforcement units are constituted by then hardened parts which are formed such that they extend in the axial direction of the driving shaft.
(13) The pair of arm sections are in elastic contact with sides of the recess of the rotary body, and the connecting section is held at the rotary body by the spring member such that the connecting section is in contact with the bottom of the recess of the rotary body.